Prenylated flavonoids from Tephrosia apollinea

In continuation of our chemical investigation on some medicinal plants of the genus Tephrosia,re-investigation of the methylenechloride/methanol(1:1) extract of the air-dried aerial part of Tephrosia apollinea afforded a new prenylated flavonoid 1, in addition to an aromatic ester,a sesquiterpene,a lignan and several known prenylated flavonoids.The structures were established by(~1H NMR,~(13)C NMR,DEPT,~1H-~1H COSY,HMQC,HMBC,NOESY and HRMS).Relative configurations of 9 and 10 were confirmed by X-ray anal...     

Measurement of strange-quark contributions to the nucleon's form factors at Q(2) = 0.230 (GeV/c)(2)

We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a Q2 of 0.230 (GeV/c)(2) and a scattering angle of theta (e) = 30 degrees - 40 degrees. Using a large acceptance fast PbF2 calorimeter with a solid angle of delta omega = 0.62 sr, the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A(phys)=(-5.44+/-0.54(stat)+/-0.26(sys))x10(-6). The standard model expectation assuming no strangeness contributions to the vector form factors is A(0) = (-6.30+/-0.43) x 10(-6). The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G(s)(E) + 0.225G(s)(M) = 0.039+/-0.034 or F(s)(1) + 0.130F(s)(2) = 0.032+/-0.028.     

Influence of carboxylated and phosphonated single-walled carbon nanotubes on the transport properties of sulfonated poly(styrene-isobutylene-styrene) membranes

This study discusses the effect of carboxylated (COOH) and phosphonated (PO₃H₂) single-walled carbon nanotubes (SWCNTs) on the transport properties of sulfonated poly(styrene-isobutylene-styrene) (SO₃H SIBS) as polymer nanocomposite membranes (PNMs) for direct methanol fuel cell (DMFC) and chemical and biological protective clothing (CBPC) applications. The properties were determined as a function of sulfonation level of SIBS, SWCNTs functionalization and loading. A comprehensive materials characterization study was performed to understand the interactions between the nanofillers and the functionalized polymer matrix, and to determine the effect of their incorporation on the resulting nanostructure of the PNMs. Results indicate that the sulfonation level is the variable that dictates nanofiller dispersion, mechanical properties, water absorption capabilities, morphology, and oxidative stability of SO₃H SIBS. Meanwhile, the nanofiller loading and functionalization influenced the transport properties. The nanofillers reduced methanol permeation. PO₃H₂ SWCNTs increased the proton conductivity but at a high sulfonation level (i.e., 90 mol %), the ionic interconnectivity caused a more complex morphology decreasing the transport of protons. Optimal selectivity in transport properties were found with a sulfonation level of 61 mol % and a PO₃H₂ SWCNTs loading of 1.0 wt. % for DMFC and 0.5 wt. % for CBPC due to changes in morphology and the unique transport mechanism of permeants through the PNMs. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2475–2495     

Equations of state for strongly anharmonic crystals with a complex lattice

On the basis of a nonsymmetrized self-consistent-field approximation, thermal and caloric equations of state for strongly anharmonic crystals with a complex lattice are considered, allowing, in principle, anharmonism of any desired (basically, even) order to be taken into account. These equations include the moments of single-particle distribution functions, which are the solutions of some system of transcendental equations. More detailed consideration is given to the case of binary crystals with strong fourth-order anharmonism. The possibility of obtaining corrections to the approximation adopted is also discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 40–44, November, 1979.     

An equilibrium ab initio atomistic thermodynamics study of chlorine adsorption on the Cu(001) surface

The effect of chlorine (Cl) chemisorption on the energetics and atomic structure of the Cu(001) surface over a wide range of chlorine pressures and temperatures has been studied using equilibrium ab initio atomistic thermodynamics to elucidate the formation of cuprous chloride (CuCl) as part of the Deacon reaction on copper metal. The calculated surface free energies show that the 1/2 monolayer (ML) c(2 × 2)-Cl phase with chlorine atoms adsorbed at the hollow sites is the most stable structure for a wide range of Cl chemical potential, in agreement with experimental observations. It is also found that at very low pressure and exposure, but elevated temperature, the 1/9 ML and 1/4 ML phases become the most stable. By contrast, a high coverage of Cl does not lead to thermodynamically stable geometries. The subsurface adsorption of Cl atoms, however, dramatically increases the stability of the 1 ML and 2 ML adsorption configurations providing a possible pathway for the formation of the bulk-chloride surface phases in the kinetic regime.     

A fiber optic biosensor for sulfite analysis in food

The sulfite fiber optic biosensor developed herein is based on the enzymatic oxidation reaction of sulfite catalyzed by sulfite oxidase (SOD). The consumption of O(2) is measured with an O(2) fiber optic sensor which monitors the fluorescence quenching of the indicator, perylene, by molecular oxygen. Perylene is immobilized into a polymer matrix and attached to the end of a fiber bundle forming an O(2) sensor. The enzyme, sulfite oxidase is immobilized on a pre-activated membrane and mounted onto the O(2) sensor. Several analytical characteristics of this sulfite biosensor were investigated including dynamic range, reversibility, reproducibility, stability and selectivity. The sulfite contents of various food samples, e.g. dried fruits, potato flakes, lemon juice were determined and the results obtained were in good agreement with the standard AOAC method.     

Conjugacy classes in sporadic simple groups

We obtain efficient programs for obtaining representatives of all the conjugacy classes of all the sporadic simple groups except the Monster and the Baby Monster.     

Q2 dependence of the neutron spin structure function g2(n) at low Q2

We present the first measurement of the Q2 dependence of the neutron spin structure function g2(n) at five kinematic points covering 0.57 (GeV/c)2 < or = Q2 < or = 1.34 (GeV/c)2 at x approximately = 0.2. Though the naive quark-parton model predicts g2 = 0, nonzero values occur in more realistic models of the nucleon which include quark-gluon correlations, finite quark masses, or orbital angular momentum. When scattering from a noninteracting quark, g2(n) can be predicted using next-to-leading order fits to world data for g1(n). Deviations from this prediction provide an opportunity to examine QCD dynamics in nucleon structure. Our results show a positive deviation from this prediction at lower Q2, indicating that contributions such as quark-gluon interactions may be important. Precision data obtained for g1(n) are consistent with next-to-leading order fits to world data.     

Evidence for strange-quark contributions to the nucleon's form factors at Q2=0.108 (GeV/c)2

We report on a measurement of the parity violating asymmetry in the elastic scattering of polarized electrons off unpolarized protons with the A4 apparatus at MAMI in Mainz at a four momentum transfer value of Q(2)=0.108 (GeV/c)(2) and at a forward electron scattering angle of 30 degrees p)=[-1.36+/-0.29(stat)+/-0.13(syst)]x10(-6). The expectation from the standard model assuming no strangeness contribution to the vector current is A(0)=(-2.06+/-0.14)x10(-6). We have improved the statistical accuracy by a factor of 3 as compared to our previous measurements at a higher Q2. We have extracted the strangeness contribution to the electromagnetic form factors from our data to be G(s)(E)+0.106G(s)(M)=0.071+/-0.036 at Q(2)=0.108 (GeV/c)(2). We again find the value for G(s)(E)+0.106G(s)(M) to be positive, this time at an improved significance level of two sigma.     

Measurement of the transverse beam spin asymmetry in elastic electron-proton scattering and the inelastic contribution to the imaginary part of the two-photon exchange amplitude

We report on a measurement of the asymmetry in the scattering of transversely polarized electrons off unpolarized protons, A( perpendicular), at two Q2 values of 0.106 and 0.230 (GeV/c)(2) and a scattering angle of 30 degrees 相似文献